Hepatitis C virus (HCV) has infected more than 170 million people worldwide. It is estimated that three to four million persons are newly infected each year, 70% of whom will develop chronic hepatitis. HCV is responsible for 50-76% of all liver cancer cases, and two thirds of all liver transplants in the developed world. Standard of Care (SOC) therapy [pegylated interferon alfa plus ribavirin (a nucleoside analog)] is only effective in 50-60% of patients and is associated with significant side-effects. Similarly, addition of a first generation HCV protease inhibitor (such as brocepravir or telaprevir) to the SOC improves outcomes and the cure rate, but the side effects are usually severe. Therefore, there is an urgent need for new HCV drugs that are potent and safe.
Hepatitis C virus genome comprises a positive-strand RNA enclosed in a nucleocapsid and lipid envelope and consists of 9.6 kb ribonucleotides and has a single open reading frame (ORP) encoding which encodes a large polypeptide of about 3,000 amino acids (Dymock et al. Antiviral Chemistry & Chemotherapy 2000, 11, 79). Following maturation, this polypeptide is cut into at least 10 proteins by cellular and viral proteases to produce the structural and non-structural (NS) proteins. In the case of HCV, the generation of mature non-structural proteins (NS2, NS3, NS4A, NS4B, NS5A, and NS5B) is effected by two viral proteases: 1) a metalloprotease that cleaves at the NS2-NS3 junction; and 2) a serine protease contained within the N-terminal region of NS3 (NS3 protease) which mediates all the subsequent cleavages downstream of NS3. The NS4A protein appears to serve multiple functions including the NS4A/NS3 complex formation, which appears to enhance the proteolytic efficiency of the NS3 protein. NS5B (also referred to herein as HCV polymerase), possesses polymerase activity and is involved in the synthesis of double-stranded RNA from the single-stranded viral RNA genome that serves as the template. NS5A is a nonstructural 56-58 kDa protein which modulates HCV replication as a component of replication complex. NS5A is highly phosphorylated by cellular protein kinases and the phosphorylation sites are conserved among HCV genotypes (Katze et al, 2001; Kim et al, 1999).
The discovery of novel antiviral strategies to selectively inhibit HCV replication has long been hindered by the lack of convenient cell culture models for the propagation of HCV (“Recent Advances in Nucleoside Monophosphate Prodrugs as Anti-hepatitis C Virus Agents” Bobeck, D. R.; Coats, S. J.; Schinazi, R. F. Antivir. Ther. 2010; Book Chapter: “Approaches for the Development of Antiviral Compounds: The Case of Hepatitis C Virus.” Raymond F. Schinazi, Steven J. Coats, Leda C. Bassit, Johan Lennerstrand, James H. Nettles, and Selwyn J. Hurwitz in: Handbook of Experimental Pharmacology, vol. 189, 25-51: Antiviral Strategies; Edited by: Hans-Georg Krausslich and Ralf Bartenschlager © Springer-Verlag Berlin Heidelberg 2009). This hurdle has been overcome first with the establishment of the HCV replicon system in 1999 (Bartenschlager, R., Nat. Rev. Drug Discov. 2002, 1, 911-916 and Bartenschlager, R., J. Hepatol. 2005, 43, 210-216) and, in 2005, with the development of robust HCV cell culture models (Wakita, T., et al., Nat. Med. 2005, 11, 791-6; Zhong, J., et al., Proc. Natl. Acad. Sci. U.S.A. 2005, 102, 9294-9; Lindenbach, B. D., et al., Science 2005, 309, 623-6).
Despite the availability of a vaccine (Crit. Rev. Clin. Lab. Sci. 2004, 41, 391-427). Yellow fever virus (YFV) continues to be a serious human health concern, causing approximately 30,000 deaths each year. YFV is one of the most lethal viral infections of humans (Expert Rev. Vaccines 2005, 4, 553-574.). Of infected individuals approximately 15% will develop severe disease, with a fatality rate of 20 to 50% among those individuals. No approved therapies specific for treatment of YFV are available. Treatment is symptomatic-rest, fluids, and ibuprofen, naproxen, acetaminophen, or paracetamol may relieve symptoms of fever and aching. Aspirin should be avoided. Although the virus is endemic to Africa and South America, there is potential for outbreaks of YFV outside these areas and such imported cases have been reported (J. Travel Med. 2005, 12(Suppl. 1), S3-S11).
West Nile Virus (WNV) is from the family Flaviviridae and predominantly a mosquito-borne disease. It was first discovered in the West Nile District of Uganda in 1937. According to the reports from the Centers for Disease Control and Prevention, WNV has been found in Africa, the Middle East, Europe, Oceania, west and central Asia, and North America. Its first emergence in North America began in the New York City metropolitan area in 1999. It is a seasonal epidemic in North America that normally erupts in the summer and continues into the fall, presenting a threat to environmental health. Its natural cycle is bird-mosquito-bird and mammal. Mosquitoes, in particular the species Culex pipiens, become infected when they feed on infected birds. Infected mosquitoes then spread WNV to other birds and mammals including humans when they bite. In humans and horses, fatal Encephalitis is the most serious manifestation of WNV infection. WNV can also cause mortality in some infected birds. There is no specific treatment for WNV infection. In cases with milder symptoms, people experience symptoms such as fever and aches that pass on their own, although even healthy people have become sick for several weeks. In more severe cases, people usually need to go to the hospital where they can receive supportive treatment.
Dengue infection is also from the family Flaviviridae and is the most important arthropod-borne infection in Singapore (Epidemiol News Bull 2006, 32, 62-6). Globally, there are an estimated 50 to 100 million cases of dengue fever (DF) and several hundred thousand cases of dengue hemorrhagic fever (DHF) per year with and average fatality fate of 5%. Many patients recover from dengue infection with minimal or no residual illness. Dengue infections are usually asymptomatic, but can present with classic dengue fever, dengue hemorrhagic fever or dengue shock syndrome. Even for outpatients, the need for maintaining adequate hydration is highly important. Dengue infections can be effectively managed by intravenous fluid replacement therapy, and if diagnosed early, fatality rates can be kept below 1%. To manage the pain and fever, patients suspected of having a dengue infection should be given acetaminophen preparations. Aspirin and non-steroidal anti-inflammatory medications may aggravate the bleeding tendency associated with some dengue infection. However, some manifestations of dengue infection previously described include liver failure (Dig Dis Sci 2005, 50, 1146-7), encephalopathy (J Trop Med Public Health 1987, 18, 398-406), and Guillain-Barré syndrome (Intern Med 2006. 45, 563-4).
Proliferative disorders are one of the major life-threatening diseases and have been intensively investigated for decades. Cancer now is the second leading cause of death in the United States, and over 500,000 people die annually from this proliferative disorder. A tumor is an unregulated, disorganized proliferation of cell growth. A tumor is malignant, or cancerous, if it has the properties of invasiveness and metastasis. Invasiveness refers to the tendency of a tumor to enter surrounding tissue, breaking through the basal laminas that define the boundaries of the tissues, thereby often entering the body's circulatory system. Metastasis refers to the tendency of a tumor to migrate to other areas of the body and establish areas of proliferation away from the site of initial appearance.
Cancer is not fully understood on the molecular level. It is known that exposure of a cell to a carcinogen such as certain viruses, certain chemicals, or radiation, leads to DNA alteration that inactivates a “suppressive” gene or activates an “oncogene.” Suppressive genes are growth regulatory genes, which upon mutation, can no longer control cell growth. Oncogenes are initially normal genes (called prooncogenes) that by mutation or altered context of expression become transforming genes. The products of transforming genes cause inappropriate cell growth. More than twenty different normal cellular genes can become oncogenes by genetic alteration. Transformed cells differ from normal cells in many ways, including cell morphology, cell-to-cell interactions, membrane content, cytoskeletal structure, protein secretion, gene expression and mortality (transformed cells can grow indefinitely).
All of the various cell types of the body can be transformed into benign or malignant tumor cells. The most frequent tumor site is lung, followed by colorectal, breast, prostate, bladder, pancreas and then ovary. Other prevalent types of cancer include leukemia, central nervous system cancers, including brain cancer, melanoma, lymphoma, erythroleukemia, uterine cancer, and head and neck cancer.
Cancer is now primarily treated with one or a combination of three means of therapies: surgery, radiation and chemotherapy. Surgery involves the bulk removal of diseased tissue. While surgery is sometimes effective in removing tumors located at certain sites, for example, in the breast, colon and skin, it cannot be used in the treatment of tumors located in other areas, such as the backbone, or in the treatment of disseminated neoplastic conditions such as leukemia.
Chemotherapy involves the disruption of cell replication or cell metabolism. It is used most often in the treatment of leukemia, as well as breast, lung, and testicular cancer. There are five major classes of chemotherapeutic agents currently in use for the treatment of cancer: natural products and their derivatives; anthacyclines; alkylating agents; antiproliferatives (also called antimetabolites); and hormonal agents. Chemotherapeutic agents are often referred to as antineoplastic agents.
Several synthetic nucleosides, such as 5-fluorouracil, have been identified that exhibit anticancer activity. 5-Fluorouracil has been used clinically in the treatment of malignant tumors, including, for example, carcinomas, sarcomas, skin cancer, cancer of the digestive organs, and breast cancer. 5-Fluorouracil, however, causes serious adverse reactions such as nausea, alopecia, diarrhea, stomatitis, leukocytic thrombocytopenia, anorexia, pigmentation and edema.
It would be advantageous to provide new antiviral and anticancer agents, compositions including these agents, and methods of treatment using these agents, particularly to treat flaviviruses, respiratory syncytial virus (RSV), influenza and cancer, and prevent the emergence of drug resistant flaviviruses, respiratory syncytial virus (RSV), influenza and cancer. The present invention provides such agents, compositions and methods.